let a = 1;
a = "aa";
a = { name: "zhangsan " };

// js变量的类型可以动态改变

let obj = { age: 18, child: { name: "lisi" } };

obj.age;

obj.age = "aaa";
obj.child = 11;

console.log(obj.age + 1); //aaa1
console.log(obj.age - 1); //NaN

// obj.child.name;

let btn = document.querySelector("#btn");
btn.onclick = function (e) {
  //
};

// document.querySelector()
// Math.ceil()

let obj2 = { name: "aa" };
obj2.nmae;

// Math.ce;
//
